A PERTH scientist's theory about dreaming pours cold water on the idea that we dream because we are distressed.

Dr George Christos says dreams serve an important biological function.

In a book to be released in Australia this month he gives scientific substance to the idea that "sleeping on it" can produce creative solutions to problems.

Until now, scientists believed scraps of stored memory, known as "spurious memories", were pruned out during sleep.

But Dr Christos's theory suggests the opposite is true  dreaming generates SMs that may be the basis of our creative ideas.

"There are all sorts of fanciful theories about why we dream, from keeping the eyes wet and the brain warm, to erection theories," he said. "But they do not incorporate all of the neurobiological, neurochemical, neurophysiological and cognitive evidence known about dream sleep."

He said SMs enabled new ideas to be generated from existing memory.

"SMs are necessary for the brain to learn something new," he said. "Without them the brain would only be able to recall already-stored information, like a tape recorder, and we wouldn't be able to adapt to new situations."